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LOGARITHMIC DATA

   The design of variable-gain radio-frequency and intermediate-frequency
amplifiers requires data in the low  current  region  and  therefore  makes
desirable a special logarithmic set of curves.  The special  sheet  for  this
application presents the characteristics for  the  remote-cutoff  type  of
pentodes on a logarithmic plate current scale, and a linear screen  voltage
scale.  Transconductance  contours  arranged  in  a  logarithmic  order  are
presented on this plot.  An  example  of  a  G-Curve  of  this  type  for  a
remote-cutoff pentode may be seen on the 6BJ6 G-Curve.
 

MIXER DATA  SHEETS

   Special data sheets are required for the multi-control-grid type  of  mixer
tubes such as the 6CS6, 6BE6, etc.  For mixer  design  it  is  necessary  to
have data showing the effect each control grid has on  the  plate  current,
as well as the data on the small-signal interaction.

  Static design of the  mixer  tube  circuit  requires  a  standard  screen
characteristic sheet for the preliminary phase of  the  design.  The  final
conversion design is accomplished with the  special  sheets,  called  con-
verter sheets (see the 6BE6  sheets).  The  converter  G-Curve  information
is presented in two sections, one of which shows  G_m1  and  e_c3  contours,
the other G_m3 and e_c1 contours, as a function of the  screen  voltage  and
the plate current.  Use of these curves is described elsewhere*.
 

MEASUREMENT OF TUBE DATA

  The current-voltage  relationships  for  the  G-Curves  measured  for  this
Manual  were recorded with an  X-Y  recorder  and  special  variable-voltage
supplies.  The  small-signal  parameters  were  measured  with  a   General
Radio  type  561D  Vacuum  Tube  Bridge.  Each  G-Curve  so  obtained  rep-
resents the average of the measurements of  a  number  of  tubes,  and  has
been correlated with other data  sources  as  well.  Although  the  curves
thus obtained consist strictly of small sample lots, the data appear to  be
adequate for all but the most stringent design problems.

  Some of  the  data  sheets  have  been  transcribed  from  extended  data
provided by the manufacturer. (See  sheets  carrying  the  statement  "Data
courtesy of General Electric Co."  for examples.  In  these  cases,  special
large-size copies were made available.)  Such  transcription  of  data  can
frequently be accomplished  because  of  the  trend  toward  improved  data
which has resulted  from  the  introduction  of  G-Curves.  The  data  have
been replotted because of the greater flexibility of use  possible  with
G-Curves.
 

G-CURVE PREPARATION

  The transcription from extended  data  to  G-Curves  can  be  made  by  the
user.  With triodes, the values of bias or plate current for a  given  plate
 

*ref - Pullen, K. A., "Design of Mixers Using Conductance Curves,"
       Electronic  Design, June 1, 1957.

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Copyright 2008 for Phyllis K. Pullen, M.D.,
by Robert J. Legg